1. Field of Invention
The invention relates to a stack structure of a fuel cell, and a manufacturing method of same.
2. Description of Related Art
A solid polymer electrolyte membrane fuel cell includes a plurality of Membrane-Electrode Assemblies (i.e., MEAs) and a plurality of separators. Each of the MEAs includes an electrolyte membrane formed of an ion-exchange membrane, an electrode (i.e., an anode, a fuel electrode) formed of a catalyst layer which is provided on one surface of the electrolyte membrane, and an electrode (i.e., a cathode, an air electrode) formed of a catalyst layer which is provided on the other surface of the electrolyte membrane. A diffusion layer is provided between the MEA and the separator on each of the anode side and the cathode side. A fuel gas passage for supplying fuel gas (i.e., hydrogen) to the anode, and an oxidizing gas passage for supplying oxidizing gas (i.e., oxygen, normally, air) to the cathode are formed in the separator. A coolant passage for supplying coolant (i.e., cooling water, normally) is further formed in the separator. A cell is formed by sandwiching the MEA between the separators. A module includes at least one cell. A cell stacked body is formed by stacking a plurality of modules. Terminals, insulators, and end plates are provided at both ends of the cell stacked body in a direction in which cells are stacked (hereinafter, referred to as a “cell stacked direction”). The cell stacked body is fastened in the cell stacked direction. A fastening member (e.g., a tension plate), which is provided outside the cell stacked body and extends in the cell stacked direction, is fixed using screw bolts/nuts. A stack is thus assembled. On the anode side of each cell, a reaction occurs in which hydrogen is decomposed into a hydrogen ion (i.e., a proton) and an electron. The hydrogen ion moves through the electrolyte membrane to the cathode side. On the cathode side of each cell, the following reaction occurs in which water is produced from oxygen, a hydrogen ion and an electron (the electron produced at the anode of the adjacent MEA reaches the cathode side through the separator, or the electron produced at the anode of the cell, which is on one end of the stack in the cell stacked direction, reaches the cathode of the cell, which is on the other end of the stack, through an external circuit). Anode side: H2→2H++2e− Cathode side: 2H++2e−+(½) O2→H2O. An adhesive agent is provided between the separators which are adjacent to each other with the electrolyte membrane therebetween, and between the separator and the electrolyte membrane, so as to bond the separators, and the separator and the electrolyte membrane, and so as to seal gaps therebetween. A cell is thus formed. A plurality of the cells is positioned and stacked so as to form a stack. Japanese Patent Laid-Open Publication No. 2000-48849 discloses a method for positioning and stacking the cells. In the method, a notched portion is provided at an edge of each separator, and the cells are stacked while making the notched portion contact a guide post which is a reference portion of an assembly jig so as not to cause displacement between the cells.
However, there exist the following problems regarding the conventional method for assembling the cell stacked body. First, the adhesive agent comes out of the gap between the separators to the notched portion when forming a cell, and the adhesive agent, which has come out, adheres to the reference portion of the assembly jig when forming a cell or a stack, which may reduce the positioning accuracy. Secondly, the separator is deformed due to a pressing load when the separator is pressed to the reference portion of the assembly jig, and the anode side separator and the cathode side separator, which are adjacent to each other with the electrolyte membrane therebetween, come into contact with each other, which may cause a short-circuit.